One of them is 35-year-old Tetsuya Sotomura. When I met him on a sweltering afternoon earlier this week he was still hard at it in a converted factory building in a north Tokyo suburb, flying high into the air, spinning and tumbling on a massive trampoline.
Back in 2008 Tetsuya placed 4th at the Beijing Olympics, just missing a bronze medal. Since then he's fought injury that put him out of London in 2012 and Rio in 2016. Tokyo was to be his last hurrah, a hometown Olympics to end his trampolining career on a high. But another year is just too much.